Process for the production of mechanical wood-pulp.



. placed a number of flint or steel balls.

U rrED STATES PATENT BEIGE.

GUY C. HOWARD, OF SEATTLE, WASHINGTON, ASSIGNOR TO HOWARD PULP PROCESS COMPANY, OF EVERETT, WA$HINGTOI I, A. CORPORATION OF WASHINGTON.

PROCESS FOR THE PRODUCTION OF MECHANICAL WOOD-FUIiP.

No Drawing.

Specification of Letters I'at'ent. I Application filed September 12, 1910. Serial No. 581,541.

Patented July 4, 1911 Production of Mechanical Wood-Pulp, of

which the following is a specification.

- This invention relates to processes for the manufacture of wood-pulp for paper-making, and especially to wood-pulp produced by mechanical or largely mechanical means.

The object of the invention is the improvement in methods of manufacture of wood-pulp whereby increased production and greater uniformity in quality of the product is eifected. The invention consists in. "the improved and advantageous manner of disintegrating the fiber-bundles and in their continued separation and subdivision-into their ultimate fibers, as will he hereinafter described and set forth in the appended claims.

In the process hereinafter described I utilize, preferably, the well-known tube mill, consisting of a revolving horizontal or slightly inclined cylinder in whichrhis ounding and rubbing action of the mass of balls rapidly reduces the size of the material being treated.

I first grade the chipped-wood, saw-dust,

or other fiber-yielding material, according to size of the constituent fiber-bundles, as by screening. The material of larger mesh is then introduced in a tube-mill containing balls of relatively heavy weight and large dimensions and is therein subjected to disintegration and reduction in size of its fiberbundles. Upon the subdivision of said fiber-bundles to a proper, though relatively incomplete, degree of fineness, the material under treatment is Withdrawn from contact with the said larger halls and further treated by. similar contact-with balls of lesser size in a separate compartment of the machlne or in'an adjacent machine. The material thus separated in comparatively small fiber-bundles, may, in turn, be furtherreduced in size by progressively reducing the weight and size of the balls to which it is subjected, the said balls being proportioned somewhat in ratio to the mean longitudinal dimensions of the fiber-bundles included therein. It is found that by maintaining arelatively small ratio between the sizes of the grinding .halls and the material being treated that an advantageous rcnding and shearing action 15 lnstituted between the individual fibers and that their mutual cohesion is destroyed without undue reduction of their fiberlength.

The occurrences affecting the fibers Within the mill during the successive stages of treatment just described are about as follows, although it is to be understood that the phases hereinafter detailed are not distinct and complete and that all the phenomcna set forth is of constant and continued occurrence throughout the grinding operations to a varying degree: In the first stage, wherein large Wood-chips or fiberbundlcs are acted upon by relatively heavy balls, I find a compressive action against the ends of the fibers, due to the relatively large area of their cross-section, causing a battering effect and loss of cohesion between the fibers and accompanied with a shearing or tearing of the fiber-bundle into smaller units. In the second stage the balls may advantageously be proportioned to have their diameters equal to or nearly so with the lengths of the fiber-bundles and inconsequence will exert more or less bending strains upon the fiber-bundles resulting in further loss of cohesion and in disintegration. A third stage wherein the balls approximate the size of medium coarse sand finally subdivides the fib'er bundles into their ultimate fibers, chiefly through their penetration between the latter and the tear: mg apart of the connective tissue. The number of such stages in the disintegration and comminuti'on of the fibers will vary according to the material utilized and the extentto which such reduction is desired. Usually two or three said operations will be sufficient to effect separation of the indi vidual fibers, although the process may obviously be applied and adapted to the-changin conditions encountered with various materials and the purposes for which the product is to be utilized. I further propose to employ in the preparation of said Woodpulp and in combination with the aforedescribed mechanical processes, certain chemical solvents, such as caustic soda, or sulfurous acid, to destroy or weaken. the cohesion of the individual fibers and to facilitate their separation by the said mechanical means. The application of said chemi- I oals may not be necessary or desirable,

" 1. A process 'for the production of woodfpulpyconsisting of subjecting a mass of her-bundles to a disintegrating and comminuting action in a tube-mill containing balls of relatively large size and weight, and progressively reducing the size and weight of the said balls in further operation on said fiber-bundles as the size of the latter are re; d e v 2. A process for the production of wood-.

"pulp, consisting of subjecting a mass of fiber-bundles to a disintegrating and comminuting action in a tube-millcontaining balls of, relatively large size and weight, progressively reducing the size and weight of the said balls in further operation on said fiber-bhndles as the size of the latter are reduced, and treating said fiber-bundles to a chemical solvent at, a selected stage of said:

process to partially destroy the cohesion ofsaid fibers. a n

3. A process for the production of woodpulp, consisting of first subjecting a quantity of fiber-bundles to the disinte rating action in a tube-mill containing bal s with a mass heavier than the contained individual fiberbundles, second, subjecting the resulting reduced fiber-bundles to similar treatment byiballs of reduced weight, and third, continuing in further like-operation .to' reduce the weights of said ballsto correspond with the progressively reducing sizes of the fiber-bundles with which employed.

fiber bundles to disintegrating action in a tube-mill containing balls of diameters larger than the lengths of the said fiber-bundles, then" subjecting the resulting reduced process forthe production of wood pulp, consisting of subjecting a quantityof fiber-bundles to similar treatment by balls I substantially equal in diameter to the lengths of said fiberbundles, and finally subjectin the resultant mass of comminuted fiber-bun les to like treatment by balls with diameters less than the lengths of said fiberbundles.

GUY C. HOWARD.

Witnesses H. BARNES, E. PETERSON. 

